Process of converting compounds of the acetylene series into compounds of the ethylene series



Patented July 9, 1940 UNITED STATES PATENT orrlcs PROCESS OF CONVERTING COMPOUNDS OF THE ACETYLENE SERIES INTO COM- POUNDS OF THE ETHYLENE saunas Louisiana No Drawing. Application March 1. 1938. Serial No. 193,296. In Germany March 24, 1937 6 Claims.

The present invention relates to a process of converting compounds of the acetylene series into compounds of the ethylene series.

It has already been proposed to convert acetylene derivatives into ethylene derivatives by treating them with aqueous suspensions of zinc dust to which copper sulphate solution'has been added. The zinc activated by precipitated copper thus reacts with water with the formation of hydrogen. This process has the objection that the hydrogenation proper requires a multiple of the calculated-amount of zinc because on the one hand the reaction proceeds incompletely and on the other hand a considerable part of the zinc is used up by the activation. passing into solution as zinc sulphate. and is thus consumed without being used for the hydrogenation. In order to obtain a satisfactory utilisation of zinc, about one third of the zinc must be replaced by copper.

We have now found that compounds of the acetylene series can be converted into compounds of the ethylene series in a considerably simpler and more advantageous manner by treating compounds 01' the acetylene series in aqueous alkaline solution with metallic zinc, preferably in fine dispersion, as it is obtained, for example, in the electrolytic production of zinc. There may also be added as activators metals capable of forming galvanic elements with the zinc. v

Contrary to expectation, only relatively small amounts of free hydrogen are formed in the hydrogenation by the present process, so that the utilisation of the zinc is very favorable.

' Moreover, the hydrogenation of the acetylene linkage proceeds only to the formation of the ethylene linkage without any appreciable formation of the corresponding saturated compounds.

Even when acetylene compounds which contain olefinic double linkages in addition to the triple linkages are hydrogenated. the hydrogenation is limited to the triple linkages. The present invention, therefore. can most advantageously be r used for the conversion of vinylacetylene into butadiene.

Among suitable activating metals which are capable of forming galvanic elements with zinc there may be mentioned for examplecopper,

50 manganese. iron, cobalt and nickel. The addition necessary for the activation is usually very small. It can be established without trouble by a simple preliminary experiment which combination is most suitable for the hydrogenation to be carried out. In most cases, the addition or an activating metal can entirelybe dispensed with.

The hydrogenation may be so conducted that the zinc passes completely into solution as zincate during the course of the process, by using the alkaline reacting substance in such an amount that the zinc hydroxide formed can be dissolved to form a zincate. It is possible to effect the regeneration of the zinc by electrolysis of these zincate solutions because in this way the zinc is obtained in so finely divided a form that it is suitable for direct re-use without further treatment. 'In many cases. for example in the production of butadiene from vinylacetylene, it is preferable to employ smaller amouniis'of the alkaline reacting substance than are thc0retically necessary for the formation of zincate. At the end of the hydrogenation the zinc employed is mainly obtained in the form of a zinc hydroxide suspension: After having filtered off the zinc hydroxide from this suspension, the filtrate may be used forthe preparation of iresh'zinc suspensions without further purification.

For the preparation of the aqueous alkaline solutions there may be used metal oxides and hydroxides which dissolve in water with an al= kaline reaction. The caustic alkalies sodium and potassium hydroxide are especially suitable. They may be used in various concentrations, for example in 20 per cent solutions, or preferably in from 4 to 6 per cent solutions. The reaction may, however. also be carried out with solutions of alkaline earth hydroxides. If desired, organic solvents which have a good solvent power for the acetylene compounds and which are not attacked under the reaction conditions may be added to the aqueous solutions, as for example aliphatic alcohols. The hydrogenation. may also be carried out in the presence of indifferent substances, as for example indifferent gases. It is often advantageous to work in the presence of dispersing or wetting substances. for example of alkyl naphthalene 'sulphonic alkali salts or the addition products of 20 molecular proportions of ethylene oxide to fatty alcohols of high molecular weight, in order to produce the most intimate possible contact between all the reactants.

Generally speaking it is sufiicient to work at atmospheric pressure and at ordinary or slightly elevated temperature, but any other pressures may be used within a wide range of temperatures.

The process may be carried out continuously. discontinuously or in a cycle. For example con tinuous operation may be effected by adding zinc dust and caustic soda solution at the upper end of the reaction tower provided with difierent rapid stirrers arranged one above another, continuously withdrawing the zinc hydroxide suspension or the zincate solution at the lower end, the gaseous acetylene compounds being led in at the lower end of the tower and the hydrogenation products withdrawn at the upper end.

The process according to this invention may be used for practically all compounds having triple carbon linkages, as for example for acetylene, phenylacetylene, vinyl acetylene, diacetylene, divinylacetylene, methylbutinol, propiolic acid, phenylpropiolic acid and many other acetylene derivatives.

The following examples will further illustrate how the said invention may be carried out in practice but the invention is not restricted to these examples.

' Example 1 Gaseous vinyl acetylene is led at ordinary temperature through a well stirred suspension of 500 grams of zinc dust in a solution of 300 grams of caustic soda in 3 liters of water at such a speed that the throughput is about 20 liters per hour. 15 grams of finely powdered iron are added in small batches during the course of the reaction. The gases escaping from the reaction solution are liquefied by cooling. The reaction is completed when large amounts of unchanged vinylacetylene appear in the final gas. There is thus obtained mainly butadiene which contains only traces of butylene, very little hydrogen and no butane at all.

Example 2 From 10 to 20 liters of acetylene are led during an hour through a well stirred suspension of 500 grams of a zinc dust obtained by electrolysis, 5 grams of iron powder and 2 grams of the condensation product of 1 molecular proportion of oleyl alcohol and 20 molecular proportions of ethylene oxide in a solution of 600 grams of sodium hydroxide in 3 liters of water. From time to time small amounts of iron powder are added. The effluent gases contain, in addition to the ethylene formed, acetylene and small amounts of hydrogen but practically no ethane.

The unconverted acetylene may be again brought into contact with the solution, if desired in a cycle.

. Example 3 2.5 liters of vinylacetylene are shaken in a shaking vessel with-a suspension of 50 grams oi. zinc dust (85 per cent obtained by electrolysis) and 1 gram of butylnaphthalene sulphonic acid sodium salt in 200 cubic centimeters of 20 per cent caustic soda solution for 20 hours at about 20 C. The final gas consists mainly of butadiene with which are mixed a little vinylacetylene and hydrogen and only traces of butylene.

If 3 liters of vinylacetylene be shaken in a flask with a mixture of 50 grams of zinc dust (85 per cent, obtained by electrolysis), 3 grams of iron powder, 3'7 grams of calcium hydroxide, 1 gram of butylnaphthalene sulphonic acid sodium salt and 200 cubic centimeters of water for several hours, the vinylacetylene is also almost completely hydrogenated to butadiene. The final gas contains only traces of butylene and varying amounts of hydrogen.

The hydrogenation may as well be carried out in a continuous operation while using a high cylindrical vessel which is provided with several horizontal bottoms. The small rooms thus formed are connected with one another only by means of small holes in order to prevent a too fast mixture of the zinc dust suspensions in the various rooms of the reaction vessel. On the other hand, the zinc dust suspension in from 4 to 6 per cent aqueous caustic soda solution is allowed to flow continuously from the upper end to the lower end of the vessel.

Gaseous vinylacetylene is continuously blown into the zinc dust suspension at the-lower end of the vessel and is hydrogenated on its way to the upper end of the vessel. At the same time fresh zinc dust suspension is added continuously at the upper end substantially as fast as the spent zinc hydroxide suspension is removed at the lower end. The gases contained therein are set free and led back into the reaction vessel.

Example 4 2 liters of vinyl acetylene are shaken for several hours in a flask with a suspension of-.50 grams of zinc dust (85 per cent, obtained by electrolysis), 2 grams of copper powder, and 1 gram of butylnaphthalene sulphonic acid sodium salt in 200 cubic centimeters of 20 per cent caustic soda solution at 20 C. The vinylacetylene is thus hydrogenated practically completely to butadiene. The final gas contains only small amounts of hydrogen and only very small traces of butylene.

A similar result is obtained by shaking 2.5 liters of vinylacetylene with a suspension of 50 grams of zinc dust (85 per cent, obtained by electrolysis) and 2 grams of manganese powder in 200 cubic centimeters of 10 per cent caustic potash solution, or by reacting 2 liters of vinylacetylene under the same conditions with a suspension of 50 grams of zinc dust (85 per cent, obtained by electrolysis) and 2 grams of cobalt powder in 200 cubic centimeters of '5 per cent caustic soda solution.

Example 5 50 grams of phenylacetylene are shaken for several hours with a suspension of 100 grams of zinc dust, 10 grams of iron powder, 1 gram of butylnaphthalene sulphonic acid sodium salt in 200 cubic centimeters of 20 per cent caustic soda solution while excluding air. There is mainly obtained styrene (boiling point at 9 millimeters (mercury gauge) =33 C.) which may be isolated by known methods. The small amount of unconverted phenylacetylene may be separated by ammoniacal silver solution.

Example 6 2 liters of vinylacetylene are shaken for several hours in a flask with a mixture consisting of 50 grams of zinc dust (75 per cent, obtained by electrolysis), 3 grams of iron powder, 1 gram of butylnaphthalene sulphonic acid sodium salt, 81 grams of magnesium oxide and 400 cubic centimeters of water. The gas thus obtained mainly consists of butadiene. very little vinylacetylene, and only traces of butylene and hydrogen.

Example 7 butylene.

What we claim is:

1. A process for the conversion of compounds of the acetylene series into those of the ethylene series which consists in treating compounds of the acetylene series in aqueous solution of metal hydroxides dissolving in water with alkaline reaction with metallic zinc.

2. A process for the conversion of compounds of the acetylene series into those of the ethylene series which consists in treating compounds of the acetylene series in an aqueous solution of an alkali metal hydroxide with zinc dust.

3. A process for the conversion of compounds of the acetylene series into those of the ethylene series which consists in treating compounds of the acetylene series in an aqueous solution of an alkali metal hydroxide with zinc dust in the presence of a dispersing agent.

4. A process for the conversion of compounds ofrthe acetylene series into those of the ethylene series which consists in treating compounds of the acetylene series in an aqueoussolution of an alkali metal hydroxide with zinc dust in the presence of a metal capable of forming galvanic elements with zinc. I

5. A process for the conversion of vinylacetylene into butadiene which consists in treating vinylacetylene in an aqueous solution of an alkali metal hydroxide with zinc dust.

.6. In a continuous process for the conversion of. vinylacetylene into butadiene the step which comprises bringing vinylacetylene into close contact with an aqueous solution of an alkali metal hydroxide and with zinc dust, continuously removing the butadiene formed, and continuously adding alkali metal hydroxide solution and zinc dust substantially as fast as they are used up.

- WALTER REPPE.

ALEXANDER ROTHHAAS. OTTO SCHMIDT. ROLF LUEHDEMANN. 

